1. Field of the Invention
The present invention relates to an ink jet printer and particularly to such an ink jet printer which can not only collect air bubbles generated in one or more ink flow passages, so as to maintain its high recording quality, and but also efficiently remove the collected air bubbles.
2. Discussion of Related Art
There has conventionally been known a tube-supply-type ink jet printer which supplies ink to a printing head mounted on a movable carriage, via a flexible tube, from an ink tank fixed in a housing. An example of this ink jet printer is disclosed by Japanese Patent Publication P2000-103084A. However, in the ink jet printer, if air bubbles (or air) are contained in the ink present in the recording head, the printing head may fail to eject the ink, or the recording quality of the head may lower.
In the tube-supply-type ink jet printer, air cannot be prevented from permeating the tube and dissolving in the ink, because of the natural property of the material used to form the tube. Thus, it has been needed to provide an air buffer chamber (or an air bubble collecting chamber) on an upstream side of the recording head, collect the air bubbles in the air buffer chamber, and remove the thus collected air bubbles.
In the ink jet printer disclosed by the above-indicated Patent Document, the printing head has, in an upper portion thereof, a manifold (i.e., an air buffer chamber or an air bubble collecting chamber), and the ink tank and a circulating pump are fixed in position in the housing. The circulating pump is driven or operated to circulate the ink from the ink tank to a first ink flow passage, then the manifold, a second ink flow passage, and again the ink tank, so that the air bubbles generated in the circulation channel are returned to the ink tank and are removed. Meanwhile, at a maintenance position in the housing, a sucking and purging device sucks ink from an ink ejecting nozzle of the recording head.
However, in the above-indicated ink jet printer, since the ink tank communicates with the atmosphere, air (or air bubbles) is likely to mix with the ink being circulated. In addition, it is needed to employ an ink returning tube for circulating the ink from the circulating pump back to the ink tank. Thus, the ink jet printer is complicated and is increased in size.
Furthermore, in the case where an ink jet printer employs a plurality of ink tanks corresponding to a plurality of color inks so as to record a full-color image, the printer needs to employ a plurality of air buffer chambers (i.e., a plurality of air bubble collecting chambers) corresponding to the ink tanks, respectively. Hence, when a maintenance operation is performed, it is needed to remove concurrently the air bubbles from all the air buffer chambers. Thus, it has been desired to finish substantially simultaneously the respective operations of removing the air bubbles from all the air buffer chambers, and thereby improve the efficiency of those operations.